This program's objective is the delineation of the structural and functional characteristics of urease, the first natural nickel metalloenzyme, from bacterial as well as plant sources, of its relation to the biologic distribution of nickel, and of the pharmacology of its hydroxamate inhibitors relative to human disease and animal nutrition. Enzyme purification by affinity chromatography as well as by conventional methods will be followed by metal-ion quantitation by atomic absorption, evaluation of binding constants and rates by isotope exchange, of subunit composition and number in dissociating agents by gel electrophoresis and ultracentrifugation, and of conformational interactions with inhibitors and substrates by circular dichroism and difference spectrophotometry. End-group analysis and reassociation experiments will be used to verify subunit estimates. Kinetics of inactivation in denaturants will be compared with those of structural alterations, and the phenomenon of chelon-blockade of urease inactivation will be explored in regard to adenosine and AMP deaminase, after devising suitable assays and gel stains. Thiol-disulfide participation in metal-binding, polymerization, inhibition, and denaturation will be monitored spectrally, and quantitated by chemical modification. Urease-hydroxamate inhibition kinetics will be followed by determination of ligand number by equilibrium dialysis and by chromatographic isolation of the labelled complex. Toxicologic studies of the aliphatic hydroxamates will be completed, and a sensitive assay devised to facilitate pharmacodynamic studies in clinical trials. These agents show promise for the treatment of hepatic coma, uremia, and sepsis or urinary-tract infections with ureolytic bacteria, such as Proteus, Aerobacter, Staphylococcus, and Mycoplasma, and as growth promoters in livestock maintained on urea-supplemented diets. Their further application requires additional information on their utility, toxicity, and mechanism of action.